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Messages - Alok Pandey

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Models / Re: Statistical downscaling of GCMs
« on: April 27, 2017, 03:34:25 PM »

In downscaling, we usually take grids which encompass the whole study area and not just the grid which falls into it. This way the minimum number of grids for the study comes out to be 4 (for one climate variable). Thus more number of variables necessitates use of PCA.

Abstract :
River piracy

Daniel H. Shugar, John J. Clague,   James L. Best, Christian Schoof, Michael J. Willis, Luke Copland & Gerard H. Roe

Article Link :

Models / Re: Statistical downscaling of GCMs
« on: April 14, 2017, 09:01:26 AM »

"There are a lot of files with different variable in NCEP-NCAR reanalysis data archive? Should i download entire files? How will we obtain NCEP -NCAR reanalysis data for the grid containing my study area."
-> No need to download entire files. NCEP-NCAR provides freedom to download specific variable (pressure, humidity,air temp etc.) of particular time scales (daily, monthly etc.) corresponding to region of interest. more information on below links :

Models / Re: Statistical downscaling of GCMs
« on: April 12, 2017, 04:17:09 PM »

"Based on my understanding from literature, in statistical downscaling, if we want future precipitation, first we have to select predictor variables (pressure, humidity,air temp etc) from NCEP-NCAR reanalysis data and precipitation as predictand (station data) for same period. Then find the relation between predictand and predictor variable in NCEP-NCAR data. Then calibrate the model and then select same predictor variables from GCM (pressure, humidity,air temp etc) and find predictand (future station data). Is this true? Or is there any change from this?"
-> The above mentioned approach is widely used. Also many agencies now provide reanalysis data (i.e. NCEP-NCAR, ERA, JRA). The main assumptions behind this approach is that the relationship between reanalysis data (predictor) and station data (predictand) will be preserved (i.e. stationary relationship) in future and thus can be used as it is on GCM data to obtain final future projections of predictand.

"Or should we relate predictor variable in NCEP- NCAR data and predictor variables in GCM?"
-> I did not understand the rationale behind this? Where will we use this relationship in the analysis?

Models / Re: Statistical downscaling of GCMs
« on: April 07, 2017, 03:18:40 PM »
My view :

1. Can the GCMs of CMIP5 project be statistically downscaled using SDSM downscaling model? (In example which in the model webpage, they have used only HADCM3)

-> Yes.

2. Metereological parameter of SWAT are precipitation, min and max temperature, wind speed, humidiy and solar radiation. Is it necessary to downscale all parameters from GCMs to use it in SWAT? Or can we use only precipitation and temperature?

->  Since all these parameters are also provided by the GCM, it is advisable or preferred (not necessarily imposed) to use  them in analysis. However if any other model provides these parameters as long term forecasts, it can be used to enhance our perspectives on uncertainties associated with the models.

3. When downloading GCM output is it necessary to download files of all variables? Or need to download only precipitation and min and max temperature?

->  Better download only those files which will be used for analysis.

4. Which is the best and simple method to statistically downscale GCM output?

->  Every method has its pros and cons. "Best" word is very subjective here. Complexity of downscaling methods can indeed be discussed. Useful Link :,706.msg2064.html#msg2064

5.  If we are using SDSM downscaling model, on what basis we have to select predictor variables?

->  Predictor variables are selected based on their strong relationships (linear and/or non-linear) with predictand. High Correlation (also supported by physics of nature) is one widely accepted measure.

P.S. Researchers are encouraged to add and/or correct points mentioned in this post.

Post your question/information / Hydrological data biases and errors
« on: March 28, 2017, 04:33:00 PM »
Article :

Abstract :

Link to article :

Post your question/information / Atmospheric Rivers
« on: December 23, 2016, 09:15:26 PM »
Atmospheric Rivers can be defined as narrow corridors of concentrated moisture suspended in the atmosphere. It is also known as rivers in the sky. Scientists found that it was responsible for the mysterious mass die-off of wild Olympia oysters in San Francisco Bay in 2011.

For more information, read the article below.

Title :

Atmospheric rivers and the mass mortality of wild oysters: insight into an extreme future?
Abstract :
Climate change is predicted to increase the frequency and severity of extreme events. However, the biological consequences of extremes remain poorly resolved owing to their unpredictable nature and difficulty in quantifying their mechanisms and impacts. One key feature delivering precipitation extremes is an atmospheric river (AR), a long and narrow filament of enhanced water vapour transport. Despite recent attention, the biological impacts of ARs remain undocumented. Here, we use biological data coupled with remotely sensed and in situ environmental data to describe the role of ARs in the near 100% mass mortality of wild oysters in northern San Francisco Bay. In March 2011, a series of ARs made landfall within California, contributing an estimated 69.3% of the precipitation within the watershed and driving an extreme freshwater discharge into San Francisco Bay. This discharge caused sustained low salinities (less than 6.3) that almost perfectly matched the known oyster critical salinity tolerance and was coincident with a mass mortality of one of the most abundant populations throughout this species' range. This is a concern, because wild oysters remain a fraction of their historical abundance and have yet to recover. This study highlights a novel mechanism by which precipitation extremes may affect natural systems and the persistence of sensitive species in the face of environmental change.

Link to the article :
Media report:

In their study titled 'Water Situation in Bengaluru' - published under the ministry of environment & forests' (MoEF's) Environment Information System (ENVIS) in September 2016, it has been reported that as much as 73 per cent of water required by Bengaluru can be obtained from rains alone. The actual demand by the domestic sector is about 20.5 TMC (Thousand Million Cubic feet) per year.

"Way back in 1800, Bengaluru's lakes had a storage capacity of 35 TMC. Our ancestors had built them and interlinked it in such a way that their storage could meet water demand for the next 200-300 years.
However, considering the current status of lakes in and around Bengaluru, they can store only about 5 TMC of water. But over the years, deposition of silt has reduced the storage capacity to a mere 1.2 TMC. There are about 81 lakes in Koramangala valley, followed by 56 in Vrishabhavathi and 46 in Hebbal valley. What is worrying is the considerable increase in built-up area around Bengaluru."

For more details read
News Report :
Technical Report :

Profile of TV Ramachandra

Post your question/information / Re: Cauvery (Kaveri) River Water Dispute
« on: October 12, 2016, 11:45:51 PM »
Hello Jay and Everyone,

Just as we were speaking our minds about water disputes and possible solutions, the Centre has come out with a draft National Water Framework Bill, 2016. It will provide for a mechanism to develop and manage river basin in an integrated manner so that every state gets "equitable" share of a river's water without violating rights of others.

National Water Framework Bill, 2016 (May Draft)

News Article on 12/10/2016

Post your question/information / Re: Cauvery (Kaveri) River Water Dispute
« on: October 11, 2016, 04:34:23 PM »
Hello Jay,

Thank you for your reply and valuable inputs.
With course of time, rivers dries out or changes its course and thus if States are built on hydrological system, then it may also create problem.
In my view, each major Indian rivers should be considered as individual system. Central board comprising mainly of hydrological and environmental scientists should be appointed for each respective river system. Their main responsibility can be optimizing water resource allocation based on existing environmental, drinking, irrigation constraints.

Post your question/information / Cauvery (Kaveri) River Water Dispute
« on: September 27, 2016, 04:17:00 PM »
The sharing of waters of the Cauvery river has been the source of a serious conflict between the two Indian states of Tamil Nadu and Karnataka. The genesis of this conflict rests in two agreements in 1892 and 1924 between the erstwhile Madras Presidency and Princely State of Mysore. The 802 kilometres (498 mi) Kaveri river has 44,000 km2 basin area in Tamil Nadu and 32,000 km2 basin area in Karnataka. Based on inflow Karnataka is demanding a renegotiated settlement based on "equitable sharing of the waters".(more data on pic attached)

The Government of India constituted a tribunal in 1990 to look into the dispute. After hearing arguments of all the parties involved for the next 16 years, the tribunal delivered its final verdict on 5 February 2007.
2007 tribunal verdict
According to verdict, Tamil Nadu gets 419 TMC of Kaveri water while Karnataka gets 270 TMC. The actual release of water by Karnataka to Tamil Nadu is to be 192 TMC annually. Further, Kerala will get 30 TMC and Puducherry 7 TMC.[32] Water to be released to Tamil Nadu according to monthly schedule as: June month (10 TMC), July (34), August (50), September (40), October (22), November (15), December (8 ), January (3), February (2.5), March (2.5), April (2.5) and May (2.5).The Tamil Nadu and Karnataka, unhappy with the decision, filed a revision petition before the tribunal seeking a review.

Article 262 of the Constitution reads as under:

Act of 1956

Source of the information :

P.S. Kindly add new information or correct discrepancies if any found. Discussion on this topic is also encouraged.

Book Title :
Observed Climate Variability and Change over the Indian Region

Editors :  Madhavan Rajeevan Nair & Shailesh Nayak

Brief Introduction : Source of the information :

Video (by Veritasium) tells us about problems in the research, p-values, significance of published articles, why P-hacking is dangerous to science, and why negative(so called boring) results are really important. I will recommend everyone interested in research activities to watch it.

Important Point :
1. A p-Value is only really valid for single measure. once you compare whole slew of variables the probability that at least on of them gives you a false positive goes way up (known as p-hacking).
2. There is no cost to things getting wrong. The cost is not getting them published.- Prof. Brian Nosek

Link to Video :

Relevant research article :

Updates from Ministry of Water Resources, River Development & Ganga Rejuvenation (last Updated on:02/03/2016)

Intra-State Links
Benefit from Interlinking of Rivers (Inter basin water transfer)

    The overall implementation of Interlinking of Rivers programme under National Perspective Plan would give benefits of 35 million hectares of irrigation, raising the ultimate irrigation potential from 140 million hectare to 175 million hectare and generation of 34000 megawatt of power, apart from the incidental benefits of flood control, navigation, water supply, fisheries, salinity and pollution control etc.

Link for the more information/updates :

Post your question/information / Restructuring the CWC and CGWB
« on: August 16, 2016, 02:21:10 PM »
Report titled "" submitted to the Water Resources Ministry by committee led by Mihir Shah(member of the erstwhile Planning Commission) proposes to subsumption of both into a new organization.

The proposed National Water Commission will be a science-led agency to advise the States on how much water they can use without affecting rivers and groundwater, taking surface- and groundwater-usage as a single entity. The CWC, established in 1945, is in charge of surface water and creating storage structures such as dams and medium-scale reservoirs. The Central Ground Water Board is tasked with managing groundwater.

News article (source) :

Other links:

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